In recent years, advances in technology, as well as ever evolving tastes in style, have led to substantial changes in the design of automobiles. One of the changes involves the power usage and complexity of the various electrical systems within automobiles, particularly alternative fuel vehicles, such as hybrid, electric, and fuel cell vehicles.
Many of the electrical components, including the electric traction motors used in electric and hybrid electric vehicles, receive electrical power from alternating current (AC) power supplies. However, the power sources (e.g., batteries) used in such applications provide only direct current (DC) power. Thus, devices known as power inverters are used to convert the DC power to AC power. Such power inverters are typically controlled using one or more feedback mechanisms, which may rely on real-time operating data including vehicle status data, vehicle throttle data, and motor position data.
Motor position data may include the current angular position of the rotor. The angular position sensor includes a rotor and a stator. The angular position sensor rotor is mounted to the electric traction motor rotor. The angular position sensor stator is mounted to a stationary support member within the electric traction motor assembly. The angular position sensor functions by the interaction of the input exciting voltage supplied to the angular position sensor and magnetic features on the angular position sensor rotor, and results in an output signal that indicates the absolute position of the electric traction motor rotor. Ideally, the sensor rotor remains stationary and fixed relative to the motor shaft. In practice, however, fabrication tolerances, manufacturing techniques, thermal cycling, and normal wear and tear can result in some movement of the sensor rotor relative to the motor shaft. Movement of the sensor rotor relative to the motor shaft can lead to sensor data errors, which are exacerbated in multi-pole motors (where a single mechanical rotation corresponds to multiple electrical rotations, which in turn multiplies the effect of sensor data errors).